China’s rapid modernization of its military, not to mention recent provocations of its neighbors, have left the Pentagon somewhat flummoxed over whether it can spend less money and still retain superiority in Asia, especially in helping Taiwan defend itself.

Years of trying to make nice with China – such as revealing how the US military operates – has yet to be reciprocated by a secretive Beijing bent on countering US military strength.

Preventing an arms race between the US and China is in both nations’ interest, especially as each faces challenges at home to create jobs. The first step is more cooperation between their militaries, such as better communication to prevent naval accidents at sea. The two can also work together to counter terrorism and sea piracy.

But it remains unclear how much the civilian leaders in China’s ruling Communist Party can restrain the ambitions of the 2.3 million-member People’s Liberation Army – and also deal with the PLA’s fears of being “encircled” by the US and its Asian allies.

Any way forward to reduce friction between a rising China and a United States trying to downsize its global role has to focus on Taiwan, the frontline of their struggle for regional supremacy. That island nation, with its own thriving democracy, is claimed by an autocratic China – so much so that the PLA keeps more than 1,000 missiles aimed at it.

During the Gates trip, China made clear that it will maintain a “red line” on any further US military sales to Taiwan. A year ago, Mr. Obama decided to sell up to $6.4 billion in weapons to Taiwan, putting a big chill in US-China military ties. And the Pentagon is now weighing whether to recommend that Taiwan be allowed to buy advanced F-16 fighter jets to counter China’s growing threat.

Gates wisely did not retreat from a longstanding US commitment to helping Taiwan’s military – a commitment in line with historic US assistance to all of Asia’s democracies.

China’s impatience in taking over Taiwan – an ambition contrary to the wishes of earlier Communist leaders to leave the issue to future generations – has to be met with American patience to retain its military role in Asia. Retrenchment of the US military in the region would only embolden hard liners in Beijing and worry American allies from Australia to Japan.

During his visit next week, Hu can come bearing a gift – namely, ways to avoid the budding arms race with the US. The PLA didn’t give that gift to Gates, making it all the more difficult for Obama as he tries to rein in the Pentagon’s 2012 budget.